Free radical photographic system containing a pyrylium dye former

ABSTRACT

WHEREIN: R1 REPRESENTS AN ALIPHATIC GROUP, AN ARYL GROUP, OR REPRESENTS TOGETHER WITH R&#39;&#39; THE NECESSARY ATOMS TO CLOSE A HOMOCYCLIC RING, R&#39;&#39; REPRESENTS HYDROGEN, A C1-C5 ALKYL GROUP, A PHENYL GROUP, OR A PHENOXY GROUP, Z1 REPRESENTS THE NECESSARY ATOMS TO CLOSE A HOMOCYCLIC RING OR RING SYSTEM. Z2 REPRESENTS THE NECESSARY ATOMS TO CLOSE A HOMOCYCLIC NUCLEUS, R2 REPRESENTS A C1-C5 ALKYL GROUP, AND N REPRESENTS 1 OR 2.   2-R2,5,6-(-Z2-)-2H-PYRAN-2-OL   R1-(CO)(N-1)-C(-R&#39;&#39;)=CH-C&lt;(=C(-OH)-Z1-) AND   A PHOTOGRAPHIC PROCESS WHEREIN A VISIBLE IMAGE IS FORMED BY IMAGE-WISE EXPOSURE TO ACTIVE ELECTROMAGNETIC RADIATION OF A RECORDING MATERIAL WHICH COMPRISES IN INTIMATE ADMIXTURE: (1) AT LEAST ONE ORGANIC POLYHALOGEN COMPOUND OF WHICH A HALOGEN CONTAINING RADICAL CAN BE SEPARATED PHOTOLYTICALLY, AND (2) AT LEAST ONE COLOUR FORMING COMPOUND CORRESPONDING TO ONE OF THE FOLLOWING GENERAL FORMULAE:

United States Patent 3,817,752 FREE RADICAL PHOTOGRAPHIC SYSTEM CON-TAINING A PYRYLIUM DYE FORMER Urbain Leopold Laridon, Wilrijk, and JozefWilly Van den Houte, Berchem, Belgium, assignors to Agfa- Gevaert N.V.,Mortsel, Belgium No Drawing. Filed Sept. 13, 1972, Ser. No. 288,780Claims priority, application Great Britain, Sept. 14, 1971,- 42,802/71Int. Cl. G03c 1/52, 5/24 US. CI. 96-48 R 18 Claims ABSTRACT OF THEDISCLOSURE A photographic process, wherein a visible image is formed byimage-wise exposure to active electromagnetic radiation of a recordingmaterial which comprises in intimate admixture:

(1) at least one organic polyhalogen compound of which a halogencontaining radical can be separated photolytically, and

(2) at least one colour forming compound corresponding to one of thefollowing general formulae:

wherein:

R represents an aliphatic group, an aryl group, or represents togetherwith R' the necessary atoms to close a homocyclic ring,

R represents hydrogen, a C -C alkyl group, a phenyl group, or a phenoxygroup,

2; represents the necessary atoms to close a homocyclic ring or ringsystem,

2,, represents the necessary atoms to close a homocyclic nucleus,

R represents a C -C alkyl group, and

n represents 1 or 2.

The invention relates to photographic recording and reproduction ofinformation and to materials suited therefor.

Free radical photography has been described already by A. Fotland in J.Photo. Sci, Vol. :18 (1970), 33-37.

A typical photosystem which has been investigated in detail comprisesleuco crystal violet, carbon tetrabromide, triphenylstibine andpolystyrene as a binder.

These materials are commercially available but must be carefully handledto prevent the production of a triphenylmethane dye during thepreparation and storage since the leuco dye bases are very sensitive tooxygen. This is a real disadvantage for handling the materials beforeand during exposure and makes it diflicult to keep the obtained imagescompletely free from background colouration.

It is an object of the present invention to provide a photographiccolour forming system of the free radical ICC type that oliers thepossibility to produce photographic materials having a particularly goodstability, printout and optical development speed.

A photosensitive composition has now been found, which is capable ofproducing directly a visible image as a result of an image-wisemodulated exposure to actinic electromagnetic radiation and of producinga visible image by the steps of (1) image-wise exposing the recordingmaterial to activating electromagnetic radiation of a dose sufiicient tobring about a latent or barely visible image and of (2) subsequentlyoverall exposing the recording material to light of the wavelength rangefor which it has been made more sensitive in the image-wise exposure,said composition comprising in admixture:

(1) at least one organic polyhalogen compound of which a halogencontaining radical can be photolytically separated and (2) at least onecolour forming compound corresponding to one of the following generalformulae (1) or wherein:

R represents an organic group, e.g. a saturated or unsaturated aliphaticgroup, e.g. an alkyl group including a substituted alkyl group, or anaryl group including a substituted aryl group, or together with IRrepresents the necessary atoms to close a homocyclic ring, e.g. acyclohexylen-Z-one R' represents hydrogen, a lower alkyl group, e.g.methyl, or a substituted lower alkyl group, e.g. benzyl, a phenyl groupincluding a substituted phenyl group or phenyloxy,

Z represents the necessary atoms to close a homocyclic ring or ringsystem including such a ring or ring system in substituted form, e.g. aphenyl group, a naphthyl group or such groups carrying in addition tothe hydroxyl group one or more substituents, e.g. a methoxy group or abenzyl group that is further substituted with a hydroxy group and aCH=CH-COR group, R having the significance as defined above,

Z represents the necessary atoms to close a homocyclic nucleus includinga substituted homocyclic nucleus e.g. a benzene or a naphthalene nucleusincluding a substituted benzene or naphthalene nucleus,

R represents a lower alkyl (C -C group, and

n represents 1 or 2.

The following Table 1 contains an illustrative list of compoundsaccording to the general formula 1) with their melting point and thecolour formed by exposure in the presence of OBr in polystyrene asbinding agent.

TABLE 1 Number Melting of the point, compound Structural formula 0.Colour 1 Yellowlslr green.

TABLE 1-Continued Number Melting of the point, compound Structuralformula 0. Colour 250 Blue om CH=CH-O o-Q 16 115 Cyan:

CH=C H-0 0 J) CH:

17 CH3 115 D0.

CH=CHC O CH:

18 139 Magenta:

CH=CHC 0 OH:

CHa on 20 Homopolymer containing recurring units of the followingformula: Yellow;

XCHz-CH L .I

The compounds of general formula (I) can be prepared e.g. according to:

Heilbron and Whitworth, J. Chem. Soc., 123, 243 (1923). C. D. Harries,Ber. 24, 3180 (1891). Decker and V. Fellenberg, Ann. 364, 21 (1909).

A suitable compound according to the general formula (II) has thefollowing structure:

the preparation of which may proceed as follows:

In a 250 ml. flask fitted with a reflux condenser and a gas inlet tubereaching nearly the bottom of the flask are introduced:

Z-hydroxy-l-naphthaledhyde g 10 Acetone ml 50 residue treated with 50m1. of methanol by means of which treatment the residue solidifies. Theobtained solid is pulverised, washed again with 50 ml. of methanol anddried. Yield: 9 g. Melting point: 200 C.

A high photosensitivity combined with a very low fog formation isobtained by the use of the compounds according to general formula I andmore particularly by those having a methoxy group in the ortho-positionto the hydroxyl group.

Suited organic polyhalogen compounds from which a halogen containingradical can be separated photolytical- 1y are within the scope of thefollowing general formula:

each of A, B, X and Y is a halogen atom of the group of chlorine,bromine or iodine, or

wherein one of said symbols A, B, X or Y represents an alkyl group,including a substituted alkyl group e.g. a halogen substituted alkylgroup, a hydroxyalkyl group or an aralkyl group e.g. benzyl, an arylgroup, a substituted aryl group or an aroyl group, and the other symbolschlorine, bromine or iodine, or wherein at least two of said symbols A,B, X or Y represent an aromatic acyl group, e.g. benzoyl, and the othersymbols chlorine, bromine or iodine.

Suitable representatives falling within the scope of that generalformula are organic halides such as carbon tetrabromide, bromoform,iodoform, hexachloroethane, hexabromoethane, pentabromoethane, 1,1,2,2tetrabromoethane, a,a,a-tribromoacetophenone and tribromoethanol.

wherein Z represents sulphur or a single bond, 7

A represents a single bond or a divalent hydrocarbon group e.g. -CH

R represents hydrogen or a lower alkyl group, e.g.

methyl,

R represents hydrogen or a lower alkyl group, e.g. methyl or ethyl,

each of Q and Q represents hydrogen or together represent the necessaryatoms to close an adjacent carbocyclic ring or ring system includingsuch ring or ring system in substituted form, preferably an aromaticring (e.g. a benzene ring) including a substituted aromatic ring e.g. ahalogen substituted (chlorine, bromine or iodine substituted) benzenering,

each of Q and Q represents hydrogen or together represent the necessaryatoms to close an adjacent carbocyclic nucleus or ring system includingsuch a ring or ring system in substituted form, preferably an aromaticring (e.g. a benzene ring) including a substituted aromatic ring e.g. ahalogen substituted (chlorine, bromine or iodine'substituted) benzenering, and

n represents 1 or 2.

The N-vinyl polymers and copolymers can be prepared by application ofone of the various known polymerization procedures, e.g., by pearloremulsion polymerization or by polymerization in solution, whereby theinitiation of the polymerization can occur by free radicals, by ionformation, or by radiation eg, with actinic light. It is to be notedthat the polymerization degree is not critical and can vary between widelimits. As far as the copolymers are concerned, it is further to benoted that the content of groups corresponding to the general formulagiven hereinbefore is not critical and, as shown furtheron in the tableof copolymers containing N-vinylcarbazole units, can vary between widelimits, say, e.g. between 20 and 95%, when the properties of thecompounds used in the preparation of the copolymers as well as therequired sensitizing and/or mechanical properties are taken intoaccount. In general, the best results are attained with copolymershaving a content of vinyl carbazole units between 40 and 90%.

The preparation of suitable poly-N-vinylcarbazoles is described, e.g.,in the German patent specifications 931,- 731-936,421-1,097,680 and1,158,367 and the United States patent specification 2,072,465. Thepreparation of poly-N-vinyl-pyrrole proceeds analogously.

The preparation of suitable N-vinylcarbazole copolymers is described inthe United Kingdom patent specification 964,875 which specification alsocontains a preparation receipt for poly(N-allylcarbazole) (R =CH and "R=H) and for poly(N-propenylcarbazole') (R =H,

The poly-N-vinyl indoles are described in the published German patentapplications 1,906,831 and 1,917,747. The poly-N-vinyldiphenylamine isdescribed in the published German patent application 2,007,692.Halogen-substituted poly-N-vinylcarbazoles are described in thepublished Japanese patent applications 7,592/68l9,751/67 and 7,591/68.

For illustrative purposes suitable vinyl copolymers containing N-vinylcarbazole units are enumerated in the following Table 2.

TABLE 2 Mole percent of Copolymer N-vinylcarbazole Copolymer ofN-vinylcarbazole and vinylidene chloride 85.4 Copolymer ofN-vinylcarbazole and 3,3,5 trimethylisononylether 93 Copolymer ofN-vinylcarbazole and vinyl acetate 88.6 Copolymer of N-vinylcarbazoleand isopropenyl acetate 94.5 Copolymer of N-vinylcarbazole and vinylstearate 37.5 Copolymer of N-vinylcarbazole and methyl acrylate 67.6Copolymer of N-vinylcarbazole and ethyl acrylate 41 Graft copolymer ofN-vinylcarbazole and ethyl acrylate 90.3 Emulsion polymer ofN-vinylcarbazole and polyethylacrylate 94.5 Copolymer ofN-vinylcarbazole and n-butyl acrylate 58.3 Copolymer of N-vinylcarbazoleand 2-ethyl hexylacrylate 51.6 Copolymer of N-vinylcarbazole andacryloxyethyldiethylamine 76.6 Copolymer of N-vinylcarbazole and vinylcinnamate 92.5 Copolymer of N-vinylcarbazole and methyl methacrylate62.7 Copolymer of N-vinylcarbazole and isobutyl methacrylate 51.8Copolymer of N-vinylcarbazole and lauryl methacrylate 77.4 Copolymer ofN-vinylcarbazole and methylacryloxyethyl diethylamine 9.7 Copolymer ofN-vinylcarbazole and acrylonitrile 88 Graft copolymer ofN-vinylcarbazole and butylaldehyde acetal of polyvinyl alcohol 30Copolymer of N-vinylcarbazole and di(2-di-chloroethyl)-vinyl phosphonate82.4 Copolymer of N-vinylcarbazole and styrene 49. Graft copolymer ofN-vinylcarbazole and polystyrene 27.3 Copolymer of N-vinylcarbazole andvinylnapl1- thalene 47.1 Copolymer of N-vinylcarbazole and anthracene-(9,10) 91.5 Copolymer of N-vinylcarbazole and 2-vinylpyridine 31.8Copolymer of N-vinylcarbazole and 4-vinylpyridine 32.4 Copolymer ofN-vinylcarbazole and N-vinylpyrrolidine 69.1 Terpolymer ofN-vinylcarbazole, acrylonitrile and styrene 2O Graft copolymer of aterpolymer of vinyl chloride,

vinyl acetate and vinyl alcohol with poly-N-vinylcarbazole 29.4 Graftcopolymer of a terpolymer of vinyl chloride,

vinyl acetate and maleic anhydride with poly-N- vinylcarbazole 55.1

A preferred photosensitive recording material according to the presentinvention contains the color forming 9 compounds andpoly-N-vinylcarbazole in a ratio b weight within the range of 80: 100 to10:400.

The N-vinylcarbazole polymers are preferably used in admixture withcarbon tetrabromide or iodoform or in a mixture of both of saidpolyhalogen compounds. Said polyhalogen compounds are preferably usedwith respect to poly-N-vinylcarbazole in a ratio by weight in the rangeof 160: 100 to 20:100.

If the above sensitizing polymers and copolymers do not serve themselvesas binding agent for the formation of a recording layer according to thepresent invention one or more other binding agents for forming aselfsupporting or supported layer are used. For that purpose preferablyhydrophobic polymers are elected that shield as much as possible toingredients from a direct contact with the atmosphere and more especiallfrom oxygen.

Particularly suitable binders for use in the present invention arehydrophobic polymers and copolymers e.g. containing styrene, vinylacetate, acrylonitrile, acrylate, methacrylate, or butadiene units,hydrophobic cellulose derivatives, phenoxy resins or polycondensates ofthe polyester type, e.g. polycarbonates.

These polymers may be used in admixture for improvement of themechanical strength or adhering power of the recording layer to itssupport when no self-supporting layer is produced.

In order to diminish the rate of spontaneous thermal color formationover long periods of time as might be encountered during storage andprocessing of the photographic materials so-called anti-foggants may beadded to the photosensitive composition. Suitable anti-foggants includesterically hindered phenols, e.g. 2,6-ditert.butyl p-cresol and otherreducing compounds or agents accepting atmospheric oxygen.

Preferred amounts of anti-fogging agent such as said cresol compoundwith respect to photosensitive carbon tetrabromide and/ or iodoform arewithin the weight ratio range of 1:100 to 2.5:100.

A dry photographic coating containing the above mentioned ingredientscan be formed by dissolving the binding agent(s) in a suitable inertsolvent, which acts as dispersing or dissolving medium for the otheringredients, and by removing the solvent from the coating composition byevaporation so that a solid photographic recording layer is left on aproperly chosen support. The supports may be of any kind encountered insilver halide photographic materials, e.g. paper and film supports, e.g.subbed and unsubbed polyethylene terephthalate ester supports.

The recording materials of the present invention containing thecolor-forming compounds of the general formulae especially incombination with polymers and copolymers containing N-vinylcarbazoleunits and that serve as binding agent show a remarkable high sensitivitto U.V. radiation. This high sensitivity is still increased when duringthe U.V. exposure the temperature of the recording layer composition israised above 40 C. A very suitable operating temperature is in the rangeof 40-70 C.

The recording materials according to the present invention are suited toproduce print-out images of different color according to the particularcolor forming compound applied.

In a particular preferred composition for forming printout prints amixture of carbon tetrabromide and iodoform is used, which yields asuperadditive sensitivity effect.

The stabilisation of the obtained prints may proceed by Washing out theresidual free radical generator with a suitable solvent or solventmixture, e.g. a hydrocarbon liquid such as petroleum ether optionallymixed with acetone, or by simply evaporating it by raising thetemperature when the compound involved is sufliciently volatile. For thelatter purpose and the high photosensitivity, carbon tetrabromide or amixture of carbon tetrabromide and iodoform is preferred. A usefulstabilisation tempera- 10 ture is in the range of to C. During the heatstabilisation an increase of the image density is obtained.

According to a preferred recording and reproduction process of thepresent invention the information-wise exposure is carried out in such away that first a latent image is produced, which subsequently istransformed into a visible dye image by means of a so-called opticaldevelopmen The optical development proceeds by overall exposing therecording layer containing the latent or barely visible image withvisible radiation that lies in the spectral absorption band of theproducts formed by the image-wise exposure and image-wise interaction ofthe photoexposed ingredients (1) and (2) of the mentioned photosensitivecomposition. In the overall exposure no light is applied to which thephotosensitive polyhalogen compound is inherently sensitive sincethereby the effect of the imagewise exposure is masked by an overallcolouration. It is advantageous to use in the optical developmentexposure a filter absorbing all the light corresponding with thewavelength range that is inherently absorbed by the ingredients of thenon-previously exposed recording layer.

The optical development effect is marketdly speeded up and the imagedensity increased by applying heat, e.g. supplied by contact with a hotbody or through infrared radiation during the overall exposure tovisible light.

The optical development speed obtains a particularly high value by theuse of poly-N-vinylcarbazole or the copolymers containingN-vinylcarbazole units in combination with the present colour formingcompounds.

The optical development speed is likewise increased by means of anorganic compound corresponding to the following general formula:

wherein:

each of R R and R (same or dilferent) represents an aryl group includinga substituted aryl group, e.g. phenyl or a phenyl group substituted witha hydroxyl group or a halogen atom, e.g. chlorine or iodine.

Compounds of that type and the prepartion thereof are described in theUnited Kingdom Patent Specification 853,880.

It is assumed that during the exposure applied in the opticaldevelopment at least a part of the overall applied light energy isvisible light absorbed by a dyestulf salt having the pyrylium structure.Said salt seems to act as a spectral sensitizing agent for a chemicalreaction between the photosensitive polyhalogen compound or radicalsformed therefrom and the colour forming compound.

According to an alternative embodiment of the optical developmenttechnique the recording material is first overall exposed toelectromagnetic radiation in order to produce non-differentially overthe whole recording layer latent dyestuif centres that afterwards areoptically developed information-wise by a sufficiently stronginformation-wise exposure in the absorption band of the dyestutfcentres. Optionally the information-wise exposure proceedssimultaneously with an overall heating, effected e.g., by an overallinfra-red exposure.

The information-wise exposure applied in the present invention may be acontact exposure of the direct or reflex type and likewise an opticalprojection exposure as is used, e.g., in an optical enlarging apparatus.The infor mation-wise exposure need not be simultaneous in all parts ofthe recording material. The exposure may be progressive in onecontinuous step as, e.g., in sound track recording, or in successiveintermittent steps provided that the required information-wise change isobtained. Thus the recording material may be scanned with an imagewisemodulated radiant energy spot of high intensity e.g. a laser beam, orthe material may be progressively exposed through a slit, e.g. tocopying light of a tubular lamp that is given a translation movementalong the original.

A recording material of the present invention being suited for therecording of information in the form of modulated ultraviolet radiationcan be used in X-ray and electron-beam recording. X-ray beams can beabsorbed in substances absorbing high energy and by means of them createso-called secondary photos, e.g. of the ultraviolet radiation energyband, and photo-electrons that are absorbed by the photosensitivepolyhalogen compound forming through its photoradicals a dyestutf saltwith the colour forming compound. Substances for high energy absorptionthat may be incorporated into the recording element contain the elementslead, mercury, bismuth, barium and/or tungsten. Lead compounds that arephotosensitive by themselves are preferred, e.g. lead monoxide, leadbromide and lead iodide.

Suitable light sources for use in a recording method of the presentinvention are ultra-violet radiation sources, xenon-gas lamps,incandescent bulbs and flash lamps. Sunlight is also suited in theoverall exposure. For the optical development an infra-red lamp emittingalso in the visible spectrum is preferably used.

Electron beam and laser beam recording proceed with the apparatus suitedfor that purpose and known to those skilled in the art.

Recording materials of the present invention are very versatile in thatby the use of a proper sensitizing agent they can be applied forcontinuous tone or halftone reproduction. They can offer very contrastyimages so that they are very suited for the reproduction of line andscreen type originals and find a successful use in a great variety ofgraphic art applications. Due to the very high resolving power of therecording materials (the dyestuffs are formed in molecularly dividedform) the recording materials of the present invention are particularlysuited for microfilm reproduction and high precision image rendering ase.g. in the production of optical mieromask masters used in themanufacturing of microelectronic circuitry.

The reflex-exposure properties of the present recording materials makethem very useful in the document reproduction sector since in areflex-contact exposure they otfer print-out images of a sufiicientlyintense spectral density.

According to a special application a recording layer as described hereinis used in conjunction with a magnetic recording layer and is moreparticularly applied to the rear side of a flexible tape supportcarrying the magnetic recording layer. When such a material is used asound track is formed in the magnetic recording layer and a visual textimage corresponding with the sound track is photographed on therecording layer of the present invention. Such a recording material thusallows the storing of optical and acoustic signals and makes it possibleto reproduce both informations simultaneously.

The present invention is illustrated by the following examples. Thepercentages and ratios are by weight unless otherwise indicated.

EXAMPLE 1 A mixture of 500 mg. of carbon tetrabromide, 20 mg. of acolour forming compound indicated by number in Table 1 and 2 mg. of2,6-di-tert.butyl-p-cresol was dissolved in 8 ml. of apoly-N-vinylcarbazole solution in methylene chloride.

The solution was coated at a thickness of 0.12 mm. onto a non-subbedpolyethylene terephthalate support and dried in the dark at roomtemperature.

Print-out processing The recording material was exposed for 2 min.through a step wedge of constant 0.15 by means of a W. high pressuremercury vapour lamp type HPL of Philips Gloeilampenfabrieken-Eindhoven(Netherlands), placed at a distance of 10 cm.

The obtained images were stabilized by means of a 3 min. heat treatmentat C.

The obtained results expressed by the number of reproduced wedge stepsare listed in the following table.

Optical development processing The same recording materials as used inthe print-out processing were exposed through a transparent lineoriginal operating with the same U.V. lamp and exposure distance andapplying for the image-wise exposure an exposure time as indicated inthe Table.

The optical development was effected by overall exposing the image-Wiseexposed recording material with a 250 w. infrared lamp of Bie andBerntsen, Copenhagen, Denmark, emitting also in the visible spectrum andplaced at a distance of 15 cm. The overall exposure time for reaching amaximum density (d equal to 1 is listed in the Table. During the overallexposure a cut-off filter was used absorbing all the light having awavelength smaller than 580 nm.

A mixture of 200 mg. of iodoform, 20 mg. of a colour forming compoundindicated by number in Table l and 2 mg. of 2,6-di-t.-butyl-p-cresol wasdissolved in 8 ml. of a 5% poly-N-vinylcarbazole solution in methylenechloride.

The solution was coated at a thickness of 0.12 mm. onto a non-subbedpolyethylene terephthalate support and dried in the dark at roomtemperature.

The recording layer was exposed for 2 min. through a step wedge ofconstant 0.15 by means of an 80 w. high pressure mercury vapour lamptype HPL of Philips placed at a distance of 10 cm.

The obtained images were stabilized by means of a 3 min. heat treatmentat 150 C.

13 The obtained results expressed by the number of reproduced wedgesteps are listed in the following table.

The present example illustrates the image density intensificationobtained by applying a heat treatment subsequent to the image-wiseexposure.

A mixture of 200 mg. of iodoform, 50 mg. of a mixture of colour formingcompounds 3 and 18 of table 1 in a 50:50 ratio and mg. of2,6-di-t.butyl-p-cresol was dissolved in 8 ml. of a 10% phenoxy polymerbinder solution in methylene chloride.

The solution was coated at a thickness of 0.12 mm. onto a baryta coatedpaper support and dried in the dark at 50 C.

The obtained recording material was exposed for 2 min. through a stepwedge with constant 0.15 by means of an -80 w. high pressure mercuryvapour lamp placed at a distance of 10 cm.

The image density obtained in the several reproduced steps was measuredbefore heating the exposed recording layer for 2 sec. at 150 C. andafter such heat treatment. The results are listed in the followingTable. The densities were measured with white light in aMacbeth-densitometer.

EXAMPLE 4 The following coating solution was applied to an unsubbedpolyethylene terephthalate support at a thickness of 0.12 mm.:

Carbon tetrabromide mg 500 2 hydroxystyryl methyl ketone (compound 18)10% solution in butanone of Eponol (a phenoxy resin prepared fromepichlorohydrin and 2,2-bis (4- hydroxyphenyl)-propane ofShell-Netherlands After drying the coating was exposed for 2 min.through a continuous tone transparency (negative) by means of an 80 w.U.V.-lamp (type HPL) held at a distance of 10 cm. The originally weakprint-out magenta image was much intensified by heating the exposedrecording material for 3 min. at 150 C.

EXAMPLE 5 The following coating solution was applied to an unsubbedpolyethylene terephthalate support at a thickness of 0.10 mm.:

Iodoform mg 100 2 hydroxy 1 naphthavinyl methyl ketone (compound 3) m 252,6 di t butyl p cresol mg 10 10% solution in methylene chloride ofEponol (Shell-Netherlands) ml 4 After drying a faintly yellow colouredlayer was obtained.

The recording layer was exposed for 1 min. through a continuous tonetransparency (negative) 'by means of an w. U.V. lamp (type HPL) held ata distance of 10 cm.

An intense blue image was obtained by heating the exposed material at 180 C. for 1 min.

Preparation of the 2-hydroxy-1-naphthavinyl methyl ketone (compound 3)In a 10 ml. flask fitted with a reflux condenser were introduced:

Acetone ml 20 2 hydroxy l naphthaldehyde g 4 and 2 g. of sodiumhydroxide dissolved in 25 ml. of water. The obtained solution wasrefluxed for 4 h. Thereupon the reaction mixture was cooled, dilutedwith ml. of water, filtered and acidified with 3 ml. of acetic acid. Ayellowish green precipitate was obtained, which was separated withsuction, washed with water and dried.

Yield g-.. 4 Melting point C..-

EXAMPLE 6 The following coating solution was applied to an unsubbedpolyethylene terephthalate support at a thickness of 0.10 mm.:

Iodoform mg 100 2 hydroxy 1 naphthavinyl methyl ketone (compound 3) mg25 Z-hydroxystyryl methyl ketone (compound 18) mg 25 10% solution ofEponol (Shell-Netherlands) in a mixture of methylene chloride and1,1,2-trichloroethane (1:1 by volume) m1- 4 After drying a faintlyyellow coating was obtained.

The recording layer was exposed for 1 min. through a continuous tonetransparency (negative) by means of an 80 w. U.V. lamp (type HPL) heldat a distance of 10 cm.

An intense purple image was obtained by heating the exposed material for1 min. at 180 C.

EXAMPLE 7 The following coating solution was applied to an unsubbedpolyethylene terephthalate support at a thickness of 0.12 mm.:

Bromalhydrate (CBr CHO.H O) mg 250 3 methoxy-Z-hydroxystyryl methylketone hydrate (compound 4) mg 60 2,6-di-t.butyl-p-cresol mg 60 5%solution of poly-N-vinylcarbazole in methylene chloride l 8 15' Afog-free magenta image was obtained by stabilisa tion for 3 min. at 150C.

The same recording layer applied to a baryta coated paper yielded animage of the same quality.

EXAMPLE 8 The following coating solution was applied to an unsubbedpolyethylene terephthalate support at a thickness of 0.12 mm.: a

After drying the recording layer was exposed for 10 see. through acontinuous tone transparency (negative) by means of an 80 w. U.V. lamp(type HPL) held at a distance of 10 cm. A latent image was obtained thatwas optically developed by overall exposing the recording layer for 3min. with a 250 w. infrared lamp (Bie and Berntsen) through a cut-01ffilter absorbing all the light of a wavelength below 540 nm. A dense fogfree magneta image was obtained. It was stabilized by heating therecording material for 3 min. at 150 C.

A same recording layer as described above but not containing saidsensitizing agent yielded by an image-wise exposure of 30 sec. and anoverall exposure of min. only a very faint magenta image.

Equally good results as with the 1,3-diphenyl-5-(4-chlorophenyl)-pyrazoline sensitizer were obtained by using 1,3diphenyl-S(4-iodophenyl)-pyrazoline or 1,3-diphenyl-5 (4-hydroxyphenyl-pyrazoline.

EXAMPLE 9 The following coating composition was applied to an unsubbedpolyethylene terephthalate support at a thickness of 0.12 mm.:

Carbon tetrabromide mg.. 120 Compound 20 of Table 1 mg 6001,1,2-trichloroethane ml 12 The applied coating was dried for 1 h. at 60C. and thereupon exposed for 2 min. through a step wedge of constant0.15 by means of an 80 w. high pressure mercury vapour lamp (type HPL)placed at a distance of cm. A yellow wedge image was obtained, which wasstabilized by heating the exposed coating for 30 sec. at 150 C.

EXAMPLE 10 The following coating composition was applied to an unsubbedpolyethylene terephthalate support at a thickness of 0.12 mm.:

Carbon tetrabromide mg 120 Compound of Table 1 mg 2001,1,2-trichloroethane ml 6 of poly-N-vinylcarb- 10% solution in CH Clazole Preparation of compound 20 I In a reaction flask were introduced:

Polyvinylacetophenone g 2.0 Salicylaldehyde ml 3.5 Dioxan ml 20 Whileshaking the flask 1 ml. of 40% solution of benzyltrimethylammoniumhydroxide in dioxan was added.

The solution turned yellow and was kept at room temperature for 24 h.Then 0.2 ml. of acetic acid was added and the reaction mixture waspoured into methanol. The polymer was separated and purified bydissolving in methylene chloride, filtering and reprecipitation inmethanol. After drying under vacuum conditions 1.8 g. of the polymericcompound 20 were obtained.

We claim:

1. A photographic process wherein a visible image is formed in arecording material which comprises in intimate admixture:

(1) at least one organic polyhalogen compound corresponding to thefollowing general formula:

wherein:

each of A, B, X and Y is chlorine, bromine and iodine, or one of A, B, Xor Y represents an alkyl group, an aryl group or an aroyl group and theothers represent chlorine, bromine or iodine, or at least two of A, B, Xor Y represent an aromatic acyl group and the others represent chlorine,bromine or iodine, and p (2) at least one color forming compoundcorresponding to one of the following general formulae:

wherein:

R represents an alkyl group, a phenyl group, a

naphthyl group, or together with R the neces-.

sary atoms to close a cyclohexanyl ring, R represents hydrogen, a C -Calkyl group, a

phenyl group or a phenoxy group, Z represents the necessary atoms toclose a phenyl or naphthyl nucleus, Z represents the necessary atoms toclose a benzene or naphthalene nucleus, R represents a C -C alkyl group,and n represents 1 or 2, said visible image being formed by the step of:imagewise exposing the recording material to activating electromagneticradiation of a dose being sufiicient to bring about a directly visibleimage, or by the steps of: imagewise exposing the recording material toactivating electromagnetic radiation of a dose sufficient to createtherein an at most barely visible image which has a spectral sensitivityin a wawelength range outside the inherent sensitivity range of theorganic polyhalogen compound, and overall exposing the imagewise exposedrecording material to light within the wavelength range to which theinitially exposed portions were made more sensitive than the initiallynon-exposed portions, to thereby increase the visibility of said image,or by the steps of: overall exposing the recording materal toelectromagnetic radiation of a dose sufiicient to bring about in therecording material an increase in spectral sensitivity in a wavelengthrange outside the inherent sensitivity range of the polyhalogencompound, and imagewise exposing the overall exposed recording materialwithin the wavelength range for which the overall exposed recordinmaterial was made more 17 sensitive in order to form a visible imagecorresponding with said imagewise exposed portions.

2. A photosensitive recording material for producing directly a visibleimage upon imagewise exposure to activating electromagnetic radiation,said material containing an intimate mixture consisting essentially of:

(1) at least one organic polyhalogen compound corresponding to thefollowing general formula:

wherein:

each of A, B, X and Y is chlorine, bromine and iodine, or one of A, B,X'or Y represents an alkyl group, an aryl group, or an aroyl group andthe others represent chlorine, bromine or iodine, or at least two of A,B, X or Y represent an aromatic acyl group and the others representchlorine, bromine or iodine, and (2) at least one color forming compoundcorresponding to one of the following general formulae (1) or (H):

R represents an alkyl group, a phenyl group, a

naphthyl group, or together with R the necessary atoms to close acyclohexyl ring,

R represents hydrogen, a C -C alkyl group, a

phenyl group of a phenoxy group,

Z represents the necessary atoms to close a phenyl or naphthyl nucleus,

Z represents the necessary atoms to close a henzene or naphthalenenucleus,

R represents a C -C alkyl group, and

n represents 1 or 2.

Z represents sulphur or a single bond,

A represents a single bond or a. divalent hydrocarbon group,

each of R and R represents hydrogen or a lower alkyl radical,

wherein:

each of Q and Q represents hydrogen or together represent the necessaryatoms to close an adjacent carbocyclic nucleus,

each of Q and Q represents hydrogen or together rep resent the necessaryatoms to close an adjacent carbocyclic nucleus, and

n represents 1 or 2.

7. A process according to claim 6, wherein said polymeric compound ispoly-N-vinylcarbazole or a copolymer containing N-vinylcarbazole units.

8. A process according to claim 1, wherein said mixture is used incombination with an organic compound having the following generalformula:

R represents hydroxyl, chlorine or iodine.

9. A process according to claim 1, wherein the recording material incombination with said mixture contains as anti-fogging agent asterically hindered phenol.

10. A photosensitive recording material according to claim 2, whereinthe compound of general formula (1) contains a methoxy group inortho-position to the hydroxyl group on the Z nucleus.

11. A photosensitive recording material according to claim 2, whereinsaid ultraviolet-sensitive compound is carbon tetrabromide or iodoform.

12. A photosensitive recording material according to claim 2, whichcontains a mixture of carbon tetrabromide and iodoform.

13. A photosensitive recording material according to claim 2, which inaddition to said mixture contains a polymeric compound containingrecurring units of the following general structure:

l Q1 Q2 wherein zole units.

15. A photosensitive recording material according to claim 2, which inaddition to said mixture contains an organic compound having thefollowing general formula:

' wherein:

R represents hydroxyl, chlorine or iodine.

'16. A photosensitive recording material according to claim 14, whereinsaid mixture is present in layer form and 20 said polymeric compound isthe sole binding agent for said layer.

References Cited UNITED STATES PATENTS Arcesi et al. 96-115 P Hartman etal. 96-90 R Hori et al 96--90 R Thomo et al. 96-115 R Van Allan et al.96-90 PC RONALD H. SMITH, Primary Examiner W. H. LOUIE, JR., AssistantExaminer 9648 QP, 90 R US. Cl. X.R.

